Question

Which of the following is the most likely explanation for hypothyroidism in a patient whose iodine level is normal?

(A) greater production of T3 than of T4

(B) hyposecretion of TSH

(C) hypersecretion of MSH

(D) a decrease in the thyroid secretion of calcitonin

Short answer

(A) The statement "greater production of T3 than of T4” is false.

(B) The statement "hyposecretion of TSH" is true.

(C) The statement "hypersecretion of MSH” is false.

(D) The statement "a decrease in the thyroid secretion of calcitonin” is false.

Step-by-step solution

Iodine

The chemical element that acts as an essential nutrient of the diet for the human body required to produce thyroid hormone is called iodine. The several uses of iodine are promoting thyroid health, improving birth weight, treating thyroid cancer, and reducing goiters risk.

Explanation of option ‘(A)’

Hypothyroidism represents a thyroid disease in which the human body does not make enough thyroid hormone due to thyroid gland failure.

Thus, the lower T3 hormone production can cause hypothyroidism.

Therefore, the given statement is false.

Explanation of option ‘(B)’

The abbreviation TSH is stated as a thyroid-stimulating hormone. The peptide hormone produced by the pituitary gland to regulate thyroid gland hormone production is called TSH.

Thus, the TSH hyposecretion causes lower thyroid hormone and results in developing hypothyroidism.

Therefore, the given statement is true.

Explanation of option ‘(C)’

The group of peptide hormones that promotes melanin (pigment providing skin protection against UV light) production and secretion can be called melanocyte-stimulating hormone (MSH).

Thus, Cushing’s syndrome and hyperpigmentation can cause MSH hypersecretion.

Therefore, the given statement is false.

Explanation of option ‘(D)’

The protein hormone secreted by parafollicular cells and regulates calcium homeostasis is called calcitonin.

Thus, the calcitonin levels are not tested during hypothyroidism detection.

Therefore, the given statement is false.